Calculating state object definitions checksums - first version.

First part towards resolving #286 (closed)

To do in next MR:

• does not detect rearrangements of members if they were not made in FC_REFLECT - add member offsets to their hashes
• some important types are not reflected (f.e. account_name_type) - find a way for compiler to tell us that we need to manually supplement them in the mechanism of type deconstruction
• does not work on chainbase indexes - multi-layered templates that are not reflected - possibly the same problem as above
• add simple tests on foo classes and templates to show how mechanism works in different situations (template/not template, reflected/not reflected, private/public members, one/many template parameters...)
• add either logging of hashing process or on-demand list of hash-influencing elements (members, their types and offsets, enum values), so it can be easily checked what changed in case some hash shows different value